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Alternatives to Lithium-Ion Batteries for Electric Vehicles

The Lithium-Ion battery has been a hot news topic in recent years, particularly when referring to its application in electric vehicles. But, for how long will Lithium-Ion be the preferred battery for electric vehicles? There are a range of new battery and energy storage technologies under development, some more mature than others.

This blog addresses the advantages and disadvantages of Lithium-Ion battery when used in Battery Electric Vehicles (BEVs) and Hybrid Electric Vehicles (HEVs) with comparison to some of those new technologies.

This Blog Argues Two Key Points:

  • Variations of Lithium Ion will continue to dominate BEV applications primarily due to low cost and continued heavy investment, but will be replaced in the long-term with longer life battery technology.
  • Ultracapacitor (or Supercapacitor) technologies will replace Lithium-Ion batteries as the preferred energy storage unit for HEV applications, as systems orientated designers create solutions that deliver greater fuel efficiency at lower cost and longer life cycles.

The author of this blog, is Managing Director of Ayata IQ, is an innovation company that has specialises in control strategy for ultracapacitor hybrid powertrain. 

The Growth Story of Lithium Ion

The last five years have seen rapid growth in the production and consumption of the lithium-ion battery. After making its mark in portable consumer electronics, the lithium-ion battery is now popular for electric vehicle applications. The benefits that contributed to the growth of the lithium-ion battery include high energy density, small memory effect and reasonable self-discharge. In simple terms lithium batteries have historically delivered more range at lower cost than any other market ready technology for electric vehicles.

In the last ten years the cost of li-ion battery applications for electric vehicles has reduced significantly due to investment, economies of scale, and a productive learning rate. It has been predicted that cost parity between electric vehicle and combustion vehicle for economy cars will be achieved between 2025-2030.  

Source: Clean Technica (2018), $100/kWh Tesla Battery Cells This Year, $100/kWh Tesla Battery Packs In 2020

The Problems with Lithium-Ion Battery in BEVs

Whilst use of Lithium-Ion batteries will continue to grow in BEV applications there are significant problems that remain unresolved.

1. Inefficient battery packs. The lithium ion battery capacity drops on average to 60% charge capacity after 1500 full cycles. To overcome this manufacturers adopt several strategies. Firstly, they do not cycle through the full capacity of the battery, this leads to battery pack being no more than 80% efficient (i.e. wasted weight & cost). Secondly, they are continuously improving the quality of cells. Finally, the most common strategy, manufacturers are simply adding more cells to the already  < 80% efficient battery pack, this means even more wasted weight & more cost.

Useable battery

Source: Battery University (2017) Driving range as a function of battery performance

2. System Cost. The cost of the lithium-ion battery as an individual component will continue to decline over the next decade, but there are additional costs to vehicle manufacturers that are often ignored by academics. These include battery management and cooling. When people are quote kWh prices it’s best to look at it from a systems level. How does the drivetrain & body compensate for the additional weight? What other components are required for an automotive grade application? What are the warranty costs for the battery?

3. Safety & Logistics. Lithium ion batteries, if charged too fast or overheated for a variety of other reasons, have a tendency to cause electronics systems in vehicles to burn due to their high energy density and chemical nature. The OEM subsequently incurs additional cost to mitigate risk and safely transport the commodity.

Investigators Review Lithium-Ion Battery Casing

Source: The Economist (2014), Investigators Review Lithium-Ion Battery Casing

4. Raw Materials. There are also problems with the supply of raw material, lithium & cobalt. Not only is it costly to mine, the market is controlled by very few suppliers. Li-ion batteries today also contain hydrofluoric acid (HF). HF is noxious, dangerous to the touch, and an inhalation danger. This can be (allegedly) profitably managed through battery-recycling programs.

5. Slow charging. Li-Ion batteries can’t charge fast thanks to high internal resistance. High internal resistance in the battery means higher currents cannot be applied to batteries without damaging the cells. A large portion of the world does not have a garage, they work busy hours, and do not have the time or interest to have a coffee for an hour whilst their car charges. Li-ion EV’s will only be viable to everyone once drivers can charge anytime & anywhere in less than 5 minutes or have a convenient and cost effective solution to charge overnight.

image

Image of India traffic. If you were these guys, would you buy an EV? Where would you charge?

Due to these barriers, it is widely accepted that HEVs (i.e. not dependent on manually charging) will be the predominant mass-market vehicle in 2035.

The Problems with Lithium-Ion Battery in HEVs

All of the problems associated with li-ion battery applications in BEVs also apply to hybrid electric vehicles (HEVs). However there are additional problems.

    • Only 60% of the battery is useable. The top 20% is unusable because even higher internal resistance restricts the current. The bottom 20% is unusable to prevent terminal failure. Therefore 40% of the battery is wasted cost and weight which must be supported by the chassis and ICE.
  • Limited energy to reduce ICE workload. Because high internal resistance and li-ion battery chemistry limits the charge current and battery operating range, there is less available energy generated to reduce the workload of the combustions engine, therefore more fuel is consumed. 

Whilst end-users buy battery-based HEVs for improved fuel economy, they do not know that battery-based HEVs are an inefficient means to save fuel. Vehicle manufactures hide these inefficiencies through light-weighting technologies that reduce vehicle mass and by avoiding alternative costs for emissions compliance.

Future of Battery Technology in BEVs

Lithium Ion will continue to dominate, for the next fifteen years, but not because it is the superior technology. Major players such as LG Chem & Samsung SDI have established distribution control through leading technology and cost reduction. With significant investment made into nanomaterials, process innovation, and distribution channels the big players will ensure a return on those investments for as long as commercially possible.

Despite this, there are sophisticated battery technologies currently in development, most of which are yet to mature and realise the benefits of heavy investment and economies of scale.

  • Solid State. Solid-state batteries have solid elements, providing several advantages: less fire-related safety issues, extended lifetime, decreased need for expensive cooling systems, and operable in an extended temperature range. The Japanese automakers are working on it. So are the Germans
Source: Toyota (2016), All Solid State Batteries

Source: Toyota (2016), All Solid State Batteries

  • Aluminium-Ion. Aluminium-Ion and Lithium-Ion batteries are very similar, except the former have an aluminium anode. They promise increased safety and faster charging time at lower cost than Lithium-Ion batteries, but there are still issues with cyclability and life span. Stanford University is a leading developer.
  • Lithium-Sulfur. Lithium-Sulfur batteries have a lithium anode and a sulfur-carbon cathode. They promise higher energy density at lower cost than Lithium-Ion batteries, but there are still issues with safety and life span. Oxis Energy is a leading developer.
  • Metal-Air. Metal-air batteries have a pure-metal anode and an ambient air cathode. This reduces the battery weight significantly. A variety of metals can be used which promises large cost reductions in raw materials. There are issues with cylability and lifetime. MIT is a leading developer.

As these technologies mature we will see the leading battery suppliers acquire, and commercialize these technologies, eventually replacing the application of Lithium-Ion battery in BEVs.

Future of Battery Technology in HEVs

Whilst some of these emerging battery technologies offer promise to BEV applications they do not solve consumers’ problems for HEV applications.

If you look at HEV powertrain from the purest sense, the goal should be to use the combustion engine and energy-storage/motor in the most efficient combination. The less work the combustion engine does when it is is not operating efficiently the more fuel will be saved. The least efficient part of the engine’s drive cycle is acceleration because the engine supplies more torque (i.e. rpm) than what is required to move the heavy vehicle.

Because all batteries (inc. solid state) cannot charge fast, the combustion engine will still provide primary propulsion for accelerations in battery-based HEVs, especially during mid-high speed accelerations. This means the combustion engine is still operating when it is least efficient to do so. 

Ultracapacitor Systems will Redefine the HEV Market

Ayata IQ’s advanced hybrid electric control strategies (AIQ) leverage the ultracapacitor (instead of a battery) as a primary power supply to deliver on the key performance requirements for HEVs.

AIQ delivers sustainable value to HEV end-users:

    • Real World Fuel Efficiency. The rapid charge capability of the ultracapacitor can be used to generate more available energy to reduce the workload of the ICE, and control strategies have proven they can adapt to almost any drive cycle or real world condition. AIQ has proven a 30% fuel save for real world application. fyi – AIQ fuel save is not dependent on braking regeneration.
    • Unrivalled Total Cost of Ownership. Ayata IQ has proven its control strategies can reduce the performance requirement of system components, thus reducing the incremental cost. Payback periods of less than 1 year are now possible for HEV application. 
    • Improve the Emissions Baseline. AIQ powered HEVs reduce the emissions output of the vehicle, creating opportunities to reduce after-treatment content and associated costs. 
    • Lightweight, the weight of AIQ is up to 75% lighter than li-ion hybrid systems.
    • Reduce Transmission Cost. AIQ powered HEVs can delete or simplify complex and expensive transmissions to reduce weight and associated costs, for example heavy duty commercial vehicles. 
  • Long-Life. Ultracapacitors can run for one million cycles compared to 1,500 cycles with existing Lithium-Ion battery technology.

Don’t believe what you are reading? Ayata IQ can prove it. Ayata IQ can simulate its control strategies onto any combination of engine fuel map and drive cycle at low cost. Get in touch!

Contact Craig Hembrow

craig@ayataiq.com

+65 8314 7092